1. Field of the Invention
The present invention relates generally to control functions in each network layer of a complex multimedia network, and more specifically to a simplified signaling protocol supporting network distributed control functions.
2. Description of the Prior Art
In a complex multimedia network, a wide range of control issues arise in each of the network layers ranging from the physical layer to the application layer. Therefore, multimedia networks require distributed control functions to be implemented between network entities. Control issues in a telecommunication network arise in the physical layer, data link layer, network layer, session layer, and application layer. Distributed control issues typically include call processing, resource allocation, capacity exchanging, routing, dynamic configuration, protection, and restoration.
A signaling channel may be established either inside or outside of a network in order to provide for the exchange of messages for control and management purposes. The signaling channel may be supported by a transmission protocol in any network layer if the protocol provides a point-to-point channel between control protocol entities across mediated nodes. A physical layer transmission protocol supports only message exchanges between physical nodes. A data link layer transmission protocol provides a channel between adjacent switches. Transmission protocols implemented over the network layer provide signaling channels between switches and between end-points.
The network layer provides a transparent means for transmitting data from a calling party to a called party. Data transmission methods used in telecommunication networks generally include connection oriented transmission methods and connectionless oriented transmission methods. In connection oriented networks (e.g., STM, ATM, SDH, or PDH), the calling party must first establish a path to a called party and reserve resources along the path before transmitting user data, and then release the path and associated resources after the transmission is terminated. In connectionless oriented networks, a special protocol is provided in the network layer (e.g., Internet Protocol (IP)). This protocol makes the network layer completely world-wide transparent. In connectionless oriented networks, a calling party delivers packages containing the address of the called party and corresponding data establishing a connection. The Internet Protocol has been used in both the Internet and Intranet. A variety of new multi-media services have been provided based on the IP infrastructure.
Therefore, transmission of user data may be supported by either a connection-oriented network or a connectionless oriented network. Likewise, a carrier of signaling messages may be supported by either a connection-oriented network or a connectionless oriented network. A signaling channel in a connection-oriented network requires the support of a protocol for establishing the signaling channel for exchanging messages. A signaling channel in an IP connectionless oriented network typically requires only the support of User Datagram Protocol (UDP).
A complex multimedia network generally includes a signaling system for carrying control messages associated with distributed control functions between protocol entities within the network. A signaling system typically supports control functions including: establishing and releasing connections; transmitting and receiving the status of endpoints and connections; testing connections; and performing remote control functions.
Conventional signaling systems include: Signaling System No. 7 (SS7) which is a signaling protocol widely used to provide message exchange between switches in telecommunication networks; digital subscriber signaling system No. 1 (DSS 1) which is a signaling protocol used in the User-Network Interface (UNI); Resource Reservation Protocol (RSVP) which is an Internet Protocol (IP) network layer signaling protocol used for session control; and session initiation protocol (SIP) which provides for end-to-end control in IP networks. Also, communication between management stations and managed networks in management protocols such as in (CMIP) common management information protocol (see ITU-T recommendation X.711), and simple network management protocol (SNMP) may be considered to be types of signaling protocols.
Typically, most switches in telecommunication networks are signaled in accordance with Common Signaling System No. 7 (SS7). User-network interface (UNI) of ISDN networks supports DSS 1. IP networks use RSVP to support QoS guaranteed multimedia services. The IP telephony and teleconference adopts the H.323 signaling function. Web-based multimedia communication on IP networks uses SIP for ordering and customizing enhanced services on the basis of HTTP services.
One common signaling system used in switches of telecommunication networks is the Common Signaling System No. 7 (SS7). The specifications of the SS7 are published by ITU-T recommendations Q.700-Q.849. The Digital Subscriber Signaling System No. 1 (DSS 1) is also a specification of ITU-T. DSS 1 is offered by the ITU-T recommendation Q.850-Q.999.
The H.323 signaling system used on IP-based networks for end-to-end controls of multimedia communication is specified by the ITU-T. Subscriber signaling fluctions in the H.323 signaling system are derived from DSS 1. The H.323 signaling system is specified by ITU-T Recommendations H.323, H.245 and H.225.0.
A signaling system used in IP-based networks for session establishment and QoS control in the network layer is Resource reSerVation Protocol (RSVP) proposed by IETF. RSVP is published by IETF in RFC 2205.
A signaling system used for session initiation in multimedia services in IP-based network is Session Initiation Protocol (SIP) defined by IETF. The protocol is described by IETF RFC 2543.
In prior art signaling protocols, network control functions are typically implemented in accordance with function-oriented methods wherein each network control function is divided into several functional components. Control information, such as control messages for implementing each of a corresponding plurality of network control functions, is typically specified in terms of the corresponding function. In a typical prior art function-oriented signaling system supporting interoperations between functional components, a protocol must be specified for each control issue. A protocol is usually specified by components including: a collection of designated primitives and parameters associated with interfaces between protocol users and protocol entities; a set of messages transmitted between protocol entities; and a set of state transition machines and associated message processing within protocol entities. In a typical prior art function-oriented signaling system, each protocol associated with a corresponding control function includes semantic dependent primitives which are uniquely specified for the corresponding control function. As an example, for a control function for establishing a logical channel across a network, xe2x80x9cconnectxe2x80x9d and xe2x80x9cdisconnectxe2x80x9d primitives are used. Because a protocol must be specified for each control issue in a typical prior art function-oriented signaling system, the number of protocols used for communication between network entities may be very large and the maintenance for the system is very difficult and complicated. This problem becomes increasingly more important as required network services increase.
For example, SS7 is designed to provide message exchange for interoperations between specific functional entities distributed in network switches. SS7 provides for establishing a signaling channel within a common signaling channel across switches for conveying messages associated with corresponding network control functions. SS7 has been widely used in single-service networks such as telephone networks. However, the bandwidth of the bearer channel is restricted to 64 KB. SS7 does not provide any mechanism for security and access control. Because interoperations between the applications over the SS7 signaling protocol (control functions) have to be designed by message, the amount of messages and control protocols over SS7 will increase exponentially in multimedia multi-service networks. However, it is difficult to implement additional interoperation and interworking between different control functions since the messages are closely related to the corresponding functional components.
DSS 1 is used for the interface between switches and end-devices. The DSS 1 functions are designed for ISDN services. It is not adequate to be a signaling protocol on IP-based multimedia multi-service networks, since the principle of DSS 1 is to define a set of Information Elements of support to all ISDN services. The messages on the DSS interface are function-oriented. Therefore, it is not possible to extend the control functions supported by the signaling protocol.
H.323 uses the same signaling mechanism as DSS 1 for interfacing with subscribers. The signaling between endpoints (terminals, gateways, and gatekeepers) for control functions is defined on the signaling channel across IP network. H.323 signaling is also a function-oriented signaling system since the messages are defined by functions and the signaling functions are associated by the control functions.
RSVP is used for resource reservation in network layer for a multicast session. The signaling mechanism of RSVP, which has an object oriented approach, provides the ability to spread large kinds of messages along the paths of a session. However, it can be used for control functions in the network layer only. It is not a protocol for end-to-end control. SIP makes use of the HTML protocols to describe the messages between clients and servers for initiating multimedia sessions. Because the servers provide session control functions, the HTML messages are still function-oriented.
Prior art signaling protocols in telecommunication networks are dependent on control functions. Therefore, each control function is defined by a specific collection of primitives, parameters, messages, state-transitions, processing and security mechanisms over message transmission functions. This feature results in a large number of complex control and signaling functions. Since the signaling systems are designed for the networks with the same technology, the interoperations between heterogeneous networks and the interworking between different network layers are difficult to be implemented. In addition, current signaling mechanisms are independent of management signaling protocols such as CMIP and SNMP. When a control needs management information (e.g., call admission needs the information of resources and policies), the interoperations between management systems and control functions are further complicated.
Object-oriented methods provide an alternative to function-oriented methods for system analysis, design, and implementation. In an object model of a system, objects are represented by a set of attributes, methods and restrictions. Objects and interactions between the objects are defined. Details of the objects are encapsulated and invisible to others.
Security is an important issue in signaling systems. Any operation on network entities should be authorized and authenticated while the signaling channel is built on a non-private network. Security mechanisms should be established in network entities for each control function whether the signaling mechanism is function-oriented or message-oriented. Operation-oriented signaling provides protection from illegal operations, and supports access controls for a specific set of objects.
FIG. 1 is a block diagram generally illustrating a community at 10 established in a network in accordance with a conventional function-oriented common signaling system including a first network entity 12 and a second network entity 14. A message channel 16, which is supported by a common signaling system, provides a platform for a plurality of distributed network control functions 18 in the network. The depicted signaling system includes three network distributed control functions 18 designated FUNCTION_A, FUNCTION_B, and FUNCTION_C, each providing distributed functions associated with the first and second network entities. The common signaling system supporting the message channel 16 provides an end-to-end channel, which may be reliable, for transferring control messages between the first and second network entities. For the case wherein the supporting platform is a connection-oriented network, the control channels must be established before the control function is available.
In order to make the distributed control functions available in a function-oriented control and signaling environment, a control protocol invoking user and a control protocol performing user associated with each of the network functions 18 are provided in each of the network entities 12 and 14. Also, an outgoing control protocol entity and an incoming control protocol entity associated with each of the network functions 18 are provided in each of the network entities 12 and 14.
The first network entity 12 includes a control protocol invoking user 20, and an outgoing control protocol entity 22 for each of the network control functions 18. The second network entity 14 includes a control protocol performing user 24, and an incoming control protocol entity 26 for each of the network control functions 18. For example, the first network entity 12 includes CONTROL PROTOCOL_A INVOKING USER, and an OUTGOING CONTROL PROTOCOL_A ENTITY for FUNCTION_A. Also, the second network entity 14 includes a CONTROL PROTOCOL_A PERFORMING USER, and an INCOMING CONTROL PROTOCOL_A ENTITY for FUNCTION_A.
The invoking user 20 and performing user 24 act either as agents of the associated one of the distributed control functions 18, or as clients of the associated one of the outgoing and incoming protocol entities 22 and 26. The invoking user 20 accepts request messages from the corresponding one of the network control functions 18 as illustrated by a line 28, and the performing user 24 of the second network entity 14 executes the requests from the first entity 12. The performing user 24 also receives a response from the corresponding function as illustrated by a line 32, and transmits the response to the protocol invoking user 20 as illustrated by the line 30.
As an example, the CONTROL PROTOCOL_A INVOKING USER and the CONTROL PROTOCOL_A PERFORMING USER are agents of the network control FUNCTION_A, and the CONTROL PROTOCOL_B INVOKING USER and CONTROL PROTOCOL_B PERFORMING USER are agents of FUNCTION_B.
The protocol entities 22 and 26 provide control and signaling services to the protocol users 20 and 24, the services being defined for each corresponding one of the network control functions 18. The implementation of the services is based on function-oriented primitives and parameters communicated between the protocol entities 22 and 26 and the protocol users 20 and 24 as illustrated by lines 40 and 42. Thus, primitives and parameters are also defined for each corresponding one of the network control functions 18. As examples, the A-function-oriented primitives and parameters are specific to FUNCTION_A, the B-function-oriented primitives and parameters are specific to FUNCTION_B, and the C-function-oriented primitives and parameters are specific to FUNCTION_B.
Each of the protocol entities 22 and 26 includes a state transit machine, or, STM, (not shown) for describing the status of the protocol entity. For each of the network control functions 18, there is a specific description for the corresponding one of the outgoing control protocol entities 22, and a specific description for the corresponding one of the incoming control protocol entities 26.
A set of function oriented messages must be defined specifically for each corresponding one of the network control functions 18. These messages are transmitted via the message channel 16 between the protocol entities 22 and 26 as illustrated by lines 44 and 46.
Thus, traditional control and signaling mechanisms are implemented function-by-function. Particular sets of primitives, parameters, state transit machines, and messages must be designated for each specific function. If the network has many distributed control functions, the signaling mechanism becomes very complicated. Therefore, conventional function-oriented common signaling systems are difficult to maintain, difficult to update, and difficult to expand.
Open Distributed Processing (ODP) provides an object-oriented approach to network control. In accordance with ODP, a network control function can be described by an object model comprising a collection of network objects and their interactions. Furthermore, an object model is able to represent many control functions in which the same group of objects is involved. From the perspective of object interoperation, ODP is a remote access method by which an object is able to interoperate with other objects transparently. The interoperations between network objects may be supported by function-oriented, message-oriented, or operation-oriented signaling mechanisms. Function-oriented signaling makes use of designated messages for each function. Using a message-oriented mechanism, all functions share a set of specific messages. In an operation-oriented mechanism, interoperations between objects share a designated set of operations and a collection of managed objects which are the maps of the network objects.
Function-oriented signaling is widely used in network control functions. An example of message-oriented signaling is DSS 1 for call processing. Usually, services provided by the message-oriented signaling are restrained by the shared messages. In the prior art, operation-oriented signaling mechanisms have not been applied to network control functions, but have been applied to network management applications only. Operation-oriented signaling is restricted by the definitions of the operations.
FIG. 2 is a block diagram generally illustrating a conventional function-oriented model at 50 for distributed network control functions, the model including: a first network entity 52 having a corresponding plurality of modules 56; and a second network entity 54 having a corresponding plurality of modules 58. In the function-oriented model, all functions of modules associated with a particular control issue are considered in a control application. For each distributed function, a corresponding pair of modules are provided in the network entities 52 and 54. For example, one of the modules 56 designated FUNCTION_A in the first network entity 52 interoperates with an associated one of the modules 58 designated FUNCTION_A in the second network entity 54.
Interoperations between the associated modules are designed in accordance with function-oriented methods. Each of the modules 56 in the first network entity communicates only with the associated one of the modules 58 in the second network entity as indicated by lines 60. Communication between corresponding ones of the modules includes transmission of primitives, parameters, and messages. In general, in prior art function oriented signaling systems, a specifically designed set of primitives, parameters, and messages must be used for the interoperation between each corresponding pair of modules.
The function-oriented model for network distributed applications is widely used in telecommunication systems. In function-oriented models, the signaling functions are closely related to the semantics of the control functions. For example, this is the case in DSS 1.
In accordance with function-oriented modeling methods, each distributed function requires a unique associated control and signaling protocol. A disadvantage associated with function-oriented modeling methods is that the number of types of protocol entities and the complexity of the protocol entities in the network increases exponentially as the media and services of the network expand.
It is an object of the present invention to provide a signaling protocol providing a common signaling service layer between message transmission functions and various distributed control and management functions in a complex multimedia network.
It is also an object of the present invention to provide a signaling protocol providing operation-oriented common signaling information services which are associated with corresponding security and access control mechanisms for distributed control and management issues on an IP-based network, wherein the signaling information services are simple, transparent, flexible, scaleable and manageable.
It is a further object of the present invention to provide such a signaling protocol wherein the common signaling information services are semantic-independent so that a variety of applications may be run on the protocol platform, which is used for carrying messages from one point to another, without any specific design of primitives, messages, and security mechanisms.
Another object of the present invention is to provide a signaling protocol which is compatible with simple network management protocol (SNMP) used in IP-based networks so that network control functions can inter-operate with management functions and the control functions are therefore manageable by network administration.
Another object of the present invention is to provide a signaling protocol which may also be used as an interworking platform for various control functions in different network layers, such as protection and restoration.
Another object of the present invention is to provide a simplified signaling mechanism for use in telecommunication networks.
Another object of the present invention is to provide a signaling protocol for network control functions which is consistent with management functions. Briefly, a presently preferred embodiment of the present invention includes a process of providing operation oriented common signaling information services for supporting a plurality of different types of network distributed signaling functions in a network. The process includes the steps of: instantiating a class of network objects in a plurality of network entities forming a community, each of the network entities in the community having at least one of the network objects of the class, the class of network objects for modeling a corresponding one of the network distributed signaling functions; and providing a transparent operation oriented interface between the network objects of the network entities of the community, the operation oriented interface enabling interoperations between the network objects.
At least one of the network objects is associated with a corresponding managed object that is mapped to the corresponding network object by public attributes of the corresponding network object. Each of the network objects includes external methods for accessing managed objects associated with other ones of the network objects via the transparent operation oriented interface. The external methods perform network operations, and are operative to invoke the performance of network operations by other ones of the network objects in the community.
The step of providing a transparent operation oriented interface includes providing an operation oriented semantic independent signaling protocol entity in each of the network entities of the community, the signaling protocol entities for generating signaling protocol messages in response to primitives and associated parameters received from the network objects, a portion of the signaling protocol messages including packaged primitives and associated parameters. The packaged primitives are operation oriented semantic independent primitives which support a plurality of different types of network distributed signaling functions. The step of providing a transparent operation oriented interface also includes transmitting the signaling layer protocol messages between the signaling protocol entities via the network.
The operation oriented semantic independent primitives are used to specify operations to be performed by selected ones of the network objects. The operations include: a get operation for accessing values of managed objects; a Set operation for alternating values of managed objects; a create object operation for creating new managed objects; a delete object operation for deleting managed objects; a notify operation for providing notification messages to remote network objects regarding network management issues; and an event operation for providing event messages to remote network objects regarding network control issues.
The operation oriented semantic independent primitives include generic primitives for indicating a type of operation to be performed by a network object, and specific primitives indicating a behavior of the operation. The generic primitives include get primitives for accessing values of managed objects, set primitives for alternating values of managed objects, create primitives for creating new managed objects, delete primitives for deleting managed objects, event primitives for providing event messages to remote network objects regarding network control issues, and notify primitives for providing notification messages to remote network objects regarding network management issues. The specific primitives include request primitives for requesting performance of a corresponding one of the operations, status primitives for indicating a status of a corresponding process, response primitives for providing a response to a get command, confirmed primitives for indicating execution and receipt of a get command, and indication primitives for indicating a status and error in a corresponding process.
An important advantage of the signaling protocol of the present invention is that it provides transparent visibility and accessibility of network objects in a community.
Another advantage of the signaling system of the present invention is that it provides a fully distributed signaling mechanism because each signaling entity residing in a network entity provides both a server and a client simultaneously in signaling services without master-slave relationship. The connectivity between two signaling entities is supported by UDP/IP protocols.
A further advantage of the signaling system of the present invention is that the signaling protocol provides semantic-independent operation-oriented common signaling information services which are abstracted from the behaviors of the operations between specific network objects. Network objects in any type of control function provide interoperation via semantic independent primitives such as Get and Set, instead of the semantic dependent primitives which are associated with specific control functions.
An additional advantage of the signaling system of the present invention is that it provides a predefined standardized management information base. Managed objects mapped from network objects in a community are defined with control protocols and management protocols while using the MIB-based signaling protocol. Therefore, every signaling entity knows the semantics and syntax of the managed objects.
Yet another advantage of the signaling system is that it provides a common platform for both signaling functions and management functions by providing for integration of signaling functions with the Internet Standard Management Framework.
A further advantage of the signaling system is that it provides an implicit common security mechanism for all control applications over the signaling protocol. The signaling system is also advantageous in that it provides implicit common community-based access control to protect against illegal access by network objects out of the community.
Yet another advantage of the signaling system of the present invention is that it supports session initiation functions for establishing sessions between endpoints before communication begins. The signaling system is also advantageous in that it supports simultaneous interoperation between the network objects residing in different network elements.
An important advantage of the signaling system is that it supports interworking across network layers. A powerful feature of the MIB-based signaling protocol presented in the invention is the signaling protocol is designed for transparent interworking between different network layers either within or without the same network entity. This is different from current layer-based signaling mechanisms such as SS7 and DSS 1. The signaling protocol of the present invention therefore unifies the interworking across layers and between network entities. On behalf of any network object in any network layer, other network objects in different network entities and different network layers are logically visible and accessible as longer the management information bases are well defined and the operations are authorized.
Yet another advantage of the signaling system of the present invention is that it supports interoperation and interworking between heterogeneous networks provided by a variety of vendors. Interoperations between network objects in heterogeneous networks can also be implemented by the signaling protocol if signaling protocol entities are configured in each network entity of the heterogeneous networks. The interworking between the network entities with different technologies (such as IP over ATM supported by SDH) for control and management purposes are greatly simplified. Since the mapping from network object to managed object is the business of the manufacturers of network entities, the interoperations between the network entities from different venders are easy to implement by the signaling protocol.
Another important advantage of the signaling system of the present invention is that it supports signaling functions in any network. The carrier of the signaling protocol in the preferred embodiment of the present invention is UDP/IP. However, the network control and management applications over the signaling protocol may be implemented in any network. Therefore, most signaling protocols in current telecommunication networks can be substituted by the MIB-based signaling protocol of the present invention if a UDP/IP network connects all network entities of signaled networks. In the scheme, the UDP/IP network acts as a signaling network for all telecommunication networks. From the experience of the Internet, the signaling network, the common UDP/IP-based signaling network supporting the signaling protocol in the invention provides advantages in cost, efficiency and reliability.
The foregoing and other objects, features, and advantages of the present invention will be apparent from the following detailed description of the preferred embodiment which makes reference to the several figures of the drawing.